The Gloria quartz-monzodiorite: isotopic and chemical evidence of arc-related magmatism in the central part of the paleoproterozoic Mineiro belt, Minas Gerais State, Brazil

The Gloria quartz-monzodiorite, one of the mafic plutons of the Paleoproterozoic Mineiro belt, is intrusive into banded gneisses, amphibolites, schists and phyllites of the Rio das Mortes greenstone belt, in the southern portion of the Sao, Francisco Craton, State of Minas Gerais, Brazil. The Gloria quartz-monzodiorite yields a SHRIMP U-Pb zircon age of 2188 +/- 29 Ma, suggesting a tectonic relationship with the pre-collisional phase of the Mineiro belt. According to the Nd isotopic evidence (epsilon(Nd(T)) = -3.4; T-DM = 2.68 Ga) the original magmas was formed by a mixture among Archean crustal material and Paleoproterozoic juvenile magma. The Gloria quartz-monzodiorite shows metaluminous and cale-alkaline tendency with intermediate K content, comparable to that of volcanic-arc rocks. The primary mineralogical assemblage was partly modified by metamorphism, dated between 2131-2121 Ma in nearby coeval plutons. Such metamorphism is significantly older than the reported metamorphic episodes of the Mineiro belt in the Quadrildtero Ferrffero region (2059-2041 Ma) in the eastern portion of the study area. This evidence, together with chemical and isotopic data from other mafic and felsic plutons coeval with the Gloria quartz-monzodiorite, indicate a tectonic and magmatic migration within the Mineiro belt from west to east.